Air conditioning has many benefits that you may not have considered. A main one is keeping your home climate controlled and comfortable for day to day activities, particularly in a country like Australia where temperatures can be high for a significant portion of the year. 

Day-to-day you may not have any problems with your aircon.  However, if you don’t perform proper AC maintenance, issues are likely to develop over time resulting in a malfunction of the air conditioning unit. One of the most common problems is leaking water. 

If you are here then you might have an aircon leaking water problem and you don’t know how to solve it. First of all, don’t panic, breathe, turn off your AC to prevent further damage, and read the following article to understand why this is happening and what you can do about it. 

Where does the water coming out of my aircon come from?

When you have an aircon, as with any other appliances in the home, you need to know how it works to ensure correct operation. 

In this case, your air conditioner unit contains an evaporator coil that cools the warm air blown over it. The sudden change in temperature can cause condensation. Condensation is essentially a change in water state, from a vapour to a liquid state. 

Condensation forms on the coil in much the same way as water droplets form on a cold bottle or glass of water on a sunny day. The same happens in air conditioners.

Inside the indoor unit of an air conditioner, there is the evaporator heat exchange coil (a.k.a. cooling coil). When the appliance is switched on, the coil fills with low-pressure liquid refrigerant.  Liquid refrigerant absorbs heat from the hot and humid air blown over the coil.  As a result, the refrigerant boils into a vapour/gas, causing the temperature of the air blown out of the unit to be cold.

During this process, water vapor in the air (humidity) condenses on the cooling coil and condensation appears. These visible water droplets fall into the drain pan of the air conditioner. The water that you might see dripping from the air conditioner should be going outside via a drain pipe.  More on this later.

What are the reasons for water coming out of the air conditioner?

If water is dripping from the outdoor air conditioner unit during heating, you don’t have to worry. This is a natural part of the reverse cycle AC process where the outdoor unit is absorbing heat from the warm, humid air outside, causing condensation on the condenser heat exchange coil.  This is the same as the evaporator coil during cooling, as previously explained.

On the other hand, if the air conditioner blows water from the indoor unit, this may be caused by other factors.  These factors require attention to restore correct AC operation and prevent further damage.

These are the most common reasons why your air conditioner is leaking water:

  • The aircon filters are dirty.
  • The air conditioner drain is clogged.
  • The pan may be damaged or rusted.
  • The AC unit may have a broken condensate pump.
  • The aircon system has low refrigerant.

Let’s explore the common causes in more depth to help you narrow down which one/s may be applicable in your case and act accordingly.

The aircon filters are dirty

One of the main reasons why air conditioners malfunction or leak water is because of accumulated dirt and matter on the air filters.

Lack of cleaning of the air filters can cause a reduction in the aircon lifespan and even the complete system breakdown. For this reason, you need to perform routine cleaning of the air conditioner filters and AC unit as a whole.

Dirty air conditioning filter

The air conditioner drain is clogged

Condensed water passes through the drain to the outdoors, where it should suitably drain away. This is a normal process, but sometimes the air conditioner drain can collect dirt, matter, and even insects, and eventually become clogged. 

Water can’t properly flow if the drain is clogged.  This can cause an AC unit malfunction. 

The solution is relatively simple.  The drain pipe needs to located and blown or sucked out so the accumulation of dirt and blocked water gets cleared out. Also, to prevent other problems from occurring, the air conditioning drain pan should be cleaned.  These tasks are best left to a professional to avoid damage to the drain, pan, unit, and/or yourself.

The air conditioner drain pan may be damaged or rusted

If you have an old air conditioner then the drain pan may be damaged or rusted.  In this case, water could be falling right through and out of the indoor unit.

To solve this issue, you can look at replacing the pan.  However, if the air conditioner is too old (~more than 12-15 years for a standard home air conditioner), it may be better to buy a whole new system to avoid other problems occurring in the relatively near future. 

The AC unit may have a broken condensate pump

If your air conditioner unit is installed on an internal wall or lower than the outdoor unit then there is possibly a condensate pump installed to pump water outside. 

However, if the pump is broken then water will not be able to be pumped outside anymore. The pump may need a clean, repair, or replacement.  To attend to the pump you will most likely need to call an expert

Keep in mind that if the air conditioner unit is installed on an external wall, with the outdoor unit at the same height or lower, chances are you have a gravity-driven drain line carrying condensate outside.  In this instance, you will not have to worry about any condensate pump issues.

Aircon leaking water

The aircon system has low refrigerant

If you see a layer of ice on the evaporator coil inside the indoor unit, you should be concerned and stop using the air conditioner immediately.  This is because if the air conditioner continues to run with low refrigerant it can damage the compressor, which is expensive to fix. You may even have to replace the whole air conditioner unit as a result.

But, why is ice produced? This can happen for two reasons; 1. low refrigerant, due to a refrigerant leak, or 2. reduced airflow over the coils that happens when air filters are clogged.

If it is due to low refrigerant, this will change the pressure in the AC system and cause the evaporator coil to freeze over. 

The good thing is that the leaking water will be a sign for you to immediately turn off the aircon unit and call the experts to solve the problem as soon as possible.  This attention can stop greater, more costly issues from occurring and save you money in the long run.